/* e_atanhf.c -- float version of e_atanh.c.
 * s_log1pf.c -- float version of s_log1p.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "math.h"
#include "float.h"

static const float one = 1.0;
static const float huges = 1e30;

static const float zero = 0.0;
static volatile float vzero = 0.0;

static const float ln2_hi =   6.9313812256e-01;    /* 0x3f317180 */
static const float ln2_lo =   9.0580006145e-06;    /* 0x3717f7d1 */
static const float two25 =    3.355443200e+07;    /* 0x4c000000 */
static const float Lp1 = 6.6666668653e-01;    /* 3F2AAAAB */
static const float Lp2 = 4.0000000596e-01;    /* 3ECCCCCD */
static const float Lp3 = 2.8571429849e-01; /* 3E924925 */
static const float Lp4 = 2.2222198546e-01; /* 3E638E29 */
static const float Lp5 = 1.8183572590e-01; /* 3E3A3325 */
static const float Lp6 = 1.5313838422e-01; /* 3E1CD04F */
static const float Lp7 = 1.4798198640e-01; /* 3E178897 */

float
log1pf(float x)
{
    float hfsq = 0, f = 0, c = 0, s = 0, z = 0, R = 0, u = 0;
    int k = 0, hx = 0, hu = 0, ax = 0;

    GET_FLOAT_WORD(hx,x);
    ax = hx&0x7fffffff;

    k = 1;
    if (hx < 0x3ed413d0) {            /* 1+x < sqrt(2)+  */
        if(ax>=0x3f800000) {        /* x <= -1.0 */
        if(x==(float)-1.0) return -two25/vzero; /* log1p(-1)=+inf */
        else return (x-x)/(x-x);    /* log1p(x<-1)=NaN */
        }
        if(ax<0x38000000) {            /* |x| < 2**-15 */
        if(two25+x>zero            /* raise inexact */
                &&ax<0x33800000)         /* |x| < 2**-24 */
            return x;
        else
            return x - x*x*(float)0.5;
        }
        if(hx>0||hx<=((int)0xbe95f619)) {
        k=0;f=x;hu=1;}        /* sqrt(2)/2- <= 1+x < sqrt(2)+ */
    }
    if (hx >= 0x7f800000) return x+x;
    if(k!=0) {
        if(hx<0x5a000000) {
        STRICT_ASSIGN(float,u,(float)1.0+x);
        GET_FLOAT_WORD(hu,u);
            k  = (hu>>23)-127;
        /* correction term */
            c  = (k>0)? (float)1.0-(u-x):x-(u-(float)1.0);
        c /= u;
        } else {
        u  = x;
        GET_FLOAT_WORD(hu,u);
            k  = (hu>>23)-127;
        c  = 0;
        }
        hu &= 0x007fffff;
        /*
         * The approximation to sqrt(2) used in thresholds is not
         * critical.  However, the ones used above must give less
         * strict bounds than the one here so that the k==0 case is
         * never reached from here, since here we have committed to
         * using the correction term but don't use it if k==0.
         */
        if(hu<0x3504f4) {            /* u < sqrt(2) */
            SET_FLOAT_WORD(u,hu|0x3f800000);/* normalize u */
        } else {
            k += 1;
        SET_FLOAT_WORD(u,hu|0x3f000000);    /* normalize u/2 */
            hu = (0x00800000-hu)>>2;
        }
        f = u-(float)1.0;
    }
    hfsq=(float)0.5*f*f;
    if(hu==0) {    /* |f| < 2**-20 */
        if(f==zero) {
        if(k==0) {
            return zero;
        } else {
            c += k*ln2_lo;
            return k*ln2_hi+c;
        }
        }
        R = hfsq*((float)1.0-(float)0.66666666666666666*f);
        if(k==0) return f-R; else
                 return k*ln2_hi-((R-(k*ln2_lo+c))-f);
    }
    s = f/((float)2.0+f);
    z = s*s;
    R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))));
    if(k==0) return f-(hfsq-s*(hfsq+R)); else
         return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
}


float
__ieee754_atanhf(float x)
{
    float t;
    int hx,ix;
    GET_FLOAT_WORD(hx,x);
    ix = hx&0x7fffffff;
    if (ix>0x3f800000)         /* |x|>1 */
        return (x-x)/(x-x);
    if(ix==0x3f800000)
        return x/zero; /*lint !e414*/
    if(ix<0x31800000&&(huges+x)>zero) return x;    /* x<2**-28 */
    SET_FLOAT_WORD(x,ix);
    if(ix<0x3f000000) {        /* x < 0.5 */
        t = x+x;
        t = (float)0.5*log1pf(t+t*x/(one-x));
    } else
        t = (float)0.5*log1pf((x+x)/(one-x));
    if(hx>=0) return t; else return -t;
}

float atanhf(float x)
{
    return __ieee754_atanhf(x);
}
